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Author Topic:   Fuel pump question
Gearhead
Gearhead

Posts: 2164
From: Vancouver Island, Great Wet North
Registered: Mar 2000

posted 07-24-2002 01:54 PM     Click Here to See the Profile for Gearhead   Click Here to Email Gearhead     Edit/Delete Message   Reply w/Quote
As some of you may know I recently did some "upgrades" to my 79 Pace Car's engine/exhaust system. I added a CompCams XE262H cam (218/224 @0.050, .493/.500 lift), 1966 Shelby GT 350 hi-rise aluminum intake, Holley 600 VS carb (67s front, 70s back, 6.5 power valve), headers, and full dual exhaust (2.5" H-pipe and 2.5" 2-chamber Flowmaster mufflers and tailpipes). The heads are stock (for now... I have plans to put on a set of 1969 351 heads with some home porting and the bigger valves in the next year or so), and the bottom end is a relatively fresh rebuild (about 6000 miles) with stock style cast flat-top pistons and stock rods and crank (not balanced).

The car runs FANTASTIC. It pulls nicely from the bottom, and really wakes up at about 3,500 rpm. The only problem that I've encountered is that it seems to stumble a bit at around 5700 rpm. The engine seems to really want to rev more (it gets to 5500 NOW), but it feels like it's running out of fuel. I'm running the stock mechanical fuel pump and stock 5/16 line, and I'm thinking that is my problem. Which pump should I upgrade to? Is it necessary to go to 3/8 line, or can I get away with the 5/16 and just a stronger mechanical pump? Which pump? Holley?

I only want to rev to 6000 rpm, max, given the limitations of the bottom end, but I just hate that nosing over at between 5,500 and 5,700, as I know the cam has the additional 300 rpm in it (more, actually, but I don't want to blow the bottom end out of the car). Any help/advice would be apprecaited!! Thanks in advance!!

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Cheers,
Ian
M&M Member #395
-------------------
'79 Mustang Indy 500 Pace Car
Ian's Pace Car Website
Vancouver Island Mustang Association Website
Indy Pace Car Registry of Mustangs Official Website

"A friend will bail you out of jail after you do something stupid... a real friend will be sitting beside you saying 'That was SO COOL!!'".

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Mike Harris
Gearhead

Posts: 122
From: Oakfield, Ga USA
Registered: Jul 2002

posted 07-24-2002 04:00 PM     Click Here to See the Profile for Mike Harris   Click Here to Email Mike Harris     Edit/Delete Message   Reply w/Quote
Your stock fuel pump "migt" have the pressure to run there but not the volume. But with the future plans you have and a higher demand for fuel, that may not always be the case. Without a doubt, I would go to the 3/8 fuel line. As far as a pump, well, ya' gotta decide if you'd rather have a mechanical or electrical. Holley and Carter make good mechanicals that will support your motor. Carter makes a street pump and a strip pump. The street pump runs 6psi and you can run it unregulated. The strip pump puts out 8psi and you'd want to regulate it down, which would be ideal given the soon to come upgrades. The Holley pump gives 7 or 7.5 psi (can't quite remember) which you could run unregulated as well. Any of these would run around $50-$60 from Summit or Jeg's. Another plus with any of these is the adjustable bottom portion to set it in the best position for your system. Then there is the tried and true Holley Blue pump. It is my choice overall. Can't say enough about it. Ya'd have to have alot of motor to need anything bigger. Hope this helps some!

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Mike Harris
MKZ Racing
home.isoa.net/~mharrisj

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Gearhead
Gearhead

Posts: 2164
From: Vancouver Island, Great Wet North
Registered: Mar 2000

posted 07-24-2002 05:02 PM     Click Here to See the Profile for Gearhead   Click Here to Email Gearhead     Edit/Delete Message   Reply w/Quote
Thanks for the reply! So, would the Holley 80 gph pump (#12-833) be enough, or should I look at getting the 110 gph (#12-327) be better? Both say that there in no need for a regulator, but I'm wondering if 110 is overkill for my little engine.

I wondered if my stock stuff would be enough when I was putting this all together... now I have my answer.

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Cheers,
Ian
M&M Member #395
-------------------
'79 Mustang Indy 500 Pace Car
Ian's Pace Car Website
Vancouver Island Mustang Association Website
Indy Pace Car Registry of Mustangs Official Website

"A friend will bail you out of jail after you do something stupid... a real friend will be sitting beside you saying 'That was SO COOL!!'".

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Mike Harris
Gearhead

Posts: 122
From: Oakfield, Ga USA
Registered: Jul 2002

posted 07-24-2002 05:16 PM     Click Here to See the Profile for Mike Harris   Click Here to Email Mike Harris     Edit/Delete Message   Reply w/Quote
Just being me, I would go with the 110, it would not be overkill and you would have the extra assurance there.

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Mike Harris
MKZ Racing
home.isoa.net/~mharrisj

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Gearhead
Gearhead

Posts: 2164
From: Vancouver Island, Great Wet North
Registered: Mar 2000

posted 07-24-2002 05:25 PM     Click Here to See the Profile for Gearhead   Click Here to Email Gearhead     Edit/Delete Message   Reply w/Quote
Ok, 110 gph it is! I guess I'll have to change the pick-up in the tank over to a 3/8" as well. Hmmm, wonder how hard that will be to do?

Thanks for the help Mike, it's much appreciated!!

Ian

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Mike Harris
Gearhead

Posts: 122
From: Oakfield, Ga USA
Registered: Jul 2002

posted 07-24-2002 10:02 PM     Click Here to See the Profile for Mike Harris   Click Here to Email Mike Harris     Edit/Delete Message   Reply w/Quote
Glad to help. The pick-up is a piece of cake, just need to be WELL ventilated and the tank washed out. But here is my suggesstion on that. Alot of radiator shops will do work on fuel tanks, atleast around here. You could get them to pull it apart, install a new pick-up, and while it is there, get the inside of the tank coated for long trouble free usage. Just a thought.

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Mike Harris
MKZ Racing
home.isoa.net/~mharrisj

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